U.S. Treasury Secretary Steven Mnuchin waits to testify before the Senate Banking Committee at hearing on Domestic and International Policy Update on Capitol Hill in Washington, DC, U.S. May 18, 2017.

Trump has promised that his economic agenda — including chopping taxes for business and individuals, and rolling back regulations that he says hurt the private sector — will help the U.S. economy overcome sluggish growth. Republicans control both houses of Congress, and that has led to high expectations of business-friendly policies and contributed to a strong run for stocks after Trump’s election in November.

However, concerns have risen that the economic agenda could grind to a halt as Congress gets set to look more deeply into the motives behind Trump’s ouster of ex-FBI Director James Comey last week.

This week, top Republican lawmakers including House Speaker Paul Ryan attempted to shift attention toward their efforts to pass tax reform. The House Ways and Means Committee is also holding a hearing Thursday morning on taxes.